A liquid crystal device can be use to create optical deformations onto a light beam and then having the deformable mirror to compensate and correct the corresponding wavefront. This method presents the disadvantage of the high cost of the device, limitations of wavefront able to generate, the loss of lights in the system, due to polarization, and the complex algorithm and wavefront reconstruction technique used. Martin Booth, Tony Wilson. Hong-Bo Sun, Taisuke Ota, and Satoshi Kawata, “Methods for the characterization of deformable membrane mirrors”, Appl. Opt. Vol. 44, No. 24, 5131-5139 (2005).
Another method is measuring the influence response of the mirror per each actuator to create an influence matrix which describes the surface of the deformable of the mirror. Then a desire wavefront can be inserted into the simulation and solve the algorithm (different techniques) to calculate the voltage vector needed to apply to the actuators to recreate the desire wavefront. This method is not precise because of the differences between mirrors and the error already introduced when the influence function is measured. Also each actuator may have different response. This method won't respond or shown mechanical limitations of the devices unless they are previously prescribed into the simulation. An example of this is software is called MrFit*, from OKO Technologies. *M. Lokev, O. Soloviev, and G. Vdovin, eds., MrFit: Deformable mirror simulator, OKO Technologies, Delft, The Netherlands, http://www.okotech.com, (2008)
A commonly used method is to replace one of the flat mirrors on the setup with a curve mirror introducing curvature to the wavefront training the deformable mirror. This method is time consuming, because of the realignment of the setup every time a mirror is replaced. Also it is very costly due to the fact that different curve mirror with good optical quality are needed in order to obtain a wider range of aberration.
Referring now to FIGS. 1 and 2, a conventional free-space laser communication system 24 as described in U.S. Patent Application Publication No. 2003/0067657 and incorporated herein by reference is directed to supporting communication for fixed line-of-sight (LOS) points between structures such as buildings 10 via space based satellites or other relays 12, also used for comm links between trains 14, airships 16, aircraft 18, ships 20, and vehicles 22. A transceiver 24 (24a and 24b) is employed at each end of a comm. link and generally includes an interface 26 with output connected to data encoder 28 via fiber optics 30, the encoded data transferred from encoder 28 to a transmitter board 32 via coax cable 34. Board 32 superimposes the data on laser beams 36a-36c (produced by sources 35a-35c) with the optical characteristics modified by deformable mirrors 38a-38c. The adjustments are needed to correct for atmospheric distortions effects. The beams then pass through an aperture 42 in telescope body 40, which also receives laser signals 44 and directs these onto beam steering mirror 46. Mirror 46 focuses received laser signals 44 onto another deformable mirror 48 that also corrects the signals, generating a corrected signal 50. System 24 also includes a wavefront sensing and processing section for adjusting the deformable mirrors, increasing the system complexity, cost, and reliability.
It would therefore be desirable to provide a method and system to characterize a deformable mirror without these disadvantages.